The present invention relates to a video signal processing apparatus which adjusts a hue of an image displayed on a display device when a video signal outputted by a video signal reception means is displayed on the display device.
In recent years, in a television image receiver, when a video signal is processed by using the digital signal processing technology, it has been increasing to adjust the hue of a display screen by using a memory, a ROM, and the like, and a circuit configuration has been increasing with this increase. So, in order to minimize the circuit configuration and to rationalize a circuit configuration, it has been desired for a video signal processing apparatus which shares circuits such as the ROM as much as possible and therefore is rationalized, and such a video signal processing apparatus has been developed.
A conventional video signal processing apparatus will be briefly described with reference to figures.
FIG. 8 is a block diagram illustrating the conventional video signal processing apparatus X. As shown in FIG. 8, the video signal processing apparatus X is provided with an address value output means 510 which outputs an address value for adjusting the hue; multipliers 501, 502, 503, and 504; adders 505 and 506; a cos xcex94xcex8 data ROM 507 which records the cos xcex94xcex8 data shown in FIG. 7(b) (hereinafter, referred as xe2x80x9cROMcos xcex94xcex8xe2x80x9d); and a sin xcex94xcex8 data ROM 508 which records the sin xcex94xcex8 data shown in FIG. 7(a) (hereinafter, referred as xe2x80x9cROMsin xcex94xcex8xe2x80x9d). Further, a hue adjustment means Y which adjusts the hue of the video signal received by a video signal reception means 511 to output to the display device 512 is composed of multipliers 501, 502, 503, and 504, and adders 505 and 506. Further, the address value which is outputted by the address value output means 510 can be freely set by a user.
The hue adjustment in the video signal processing apparatus X so constructed will be described with reference to figures.
A video signal contains two color difference signals, that is, a B-Y signal and an R-Y signal. Then, though the hue is decided by these two signals, this is shown by a coordinate where a B-Y signal and a R-Y signal are regarded on an axis of abscissa and on an axis of ordinate, respectively, as shown in FIG. 2. In FIG. 2, xcex8 shows the original states of the inputted color difference signals, and the coordinate of the signal which is composed of the R-Y signal and the B-Y signal which are the inputted color difference signals. Further, how much the user changes the hue from this original state, that is, the amount of the change corresponds to xcex94xcex8. (Here, it is also expressed as xe2x80x9cto twist a huexe2x80x9d that the user changes the hue). Then, as shown in FIG. 2, the hue is, for example, shown such as a point A and a point B. Incidentally, it is xcex8=0 in the case of blue, the coordinate of which becomes (A, 0), and it is xcex8=90 in the case of red, the coordinate of which becomes (0, A). Hereinafter, the coordinate of the A point (starting point) and the coordinate of the B point (correction point) are represented as ({R-Y}a,{B-Y}a) and ({R-Y}b,{B-Y}b), respectively. The following relational expressions stand between these coordinates:
{R-Y}b={R-Y}axc3x97cos xcex94xcex8+{B-Y}axc3x97sin xcex94xcex8xe2x80x83xe2x80x83(1) 
{B-Y}b={B-Y}axc3x97cos xcex94xcex8xe2x88x92{R-Y}axc3x97sin xcex94xcex8xe2x80x83xe2x80x83(2) 
Therefore, for example in FIG. 2, it can be said that the video signal processing apparatus X should perform the operation of moving the hue shown by the A point to the B point. Further, the calculations of the above-described formulae (1) and (2) are performed in the hue adjustment means Y. Hereinafter, the operation of the video signal processing apparatus X will be described.
While the address value S501 outputted by the address value output means 510 is set by user, this address value S501 is inputted to ROMcos xcex94xcex8 507 and ROMsin xcex94xcex8 508, respectively. In the ROMcos xcex94xcex8 507, data corresponding to the inputted address value S501 is decided by cos xcex94xcex8 data shown in FIG. 7(b) to be outputted as an output signal S504. Similarly in ROMsin xcex94xcex8 508, data corresponding to the inputted address value S501 is decided by sin xcex94xcex8 data shown in FIG. 7(a) to be outputted as an output signal S505. These data are inputted to the hue adjustment means Y, that is, multipliers 501, 502, 503, and 504, and adders 505 and 506. Then, the calculations of the above-described formulae (1) and (2) are performed in this hue adjustment means Y, and the processed data is outputted as a modified R-Y signal S506 and a modified B-Y signal S507, in addition to the R-Y signal S502 and the B-Y signal S503 which are inputted to the hue adjustment means Y.
For example, in case where the inputted address value is (00) in a hexadecimal number notation (hereinafter, the same notation is employed), when this is inputted to ROMcos xcex94xcex8 507 and ROMsin xcex94xcex8 508 as the address signal S501, the output signal S505 (=sin xcex94xcex8) becomes xe2x80x9c0xe2x80x9d, and the output signal S504 (=cos xcex94xcex8) becomes xe2x80x9c1xe2x80x9d according to FIGS. 7(a) and 7 (b). When these are inputted to the above-described formulae (1) and (2), it results as follows:
{R-Y}b={R-Y}axc3x971+{B-Y}axc3x970={R-Y}axe2x80x83xe2x80x83(3) 
{B-Y}b={B-Y}axc3x971xe2x88x92{R-Y}axc3x970={B-Y}axe2x80x83xe2x80x83(4) 
Therefore, the inputted signals are outputted as they are. In other words, the coordinate of the B point is equal to that of the A point, meaning that the A point is equal to the B point. This means that a correction point does not exist and that there is no change in the hue.
Next, a description will be given of a case where the phase is rotated by 90 degrees. In case where the inputted address value is (40), this is inputted to ROMcos xcex94xcex8 507 and ROMsin xcex94xcex8 508 as the address signal S501, whereby the output signal S505 becomes xe2x80x9c1xe2x80x9d and the output signal S504 becomes xe2x80x9c0xe2x80x9d, respectively, according to FIGS. 7(a) and 7(b). When these are inputted to the above-described formulae (1) and (2), it results as follows:
{R-Y}b={R-Y}axc3x970+{b-Y}axc3x971={B-Y}axe2x80x83xe2x80x83(5) 
{B-Y}b={B-Y}axc3x970xe2x88x92{R-Y}axc3x971={R-Y}axe2x80x83xe2x80x83(6) 
Therefore, it is understood that the phase has rotated by 90 degrees from the A point.
However, the video signal processing apparatus X as described above results in that the whole circuit size becomes large because two kinds of ROMs, the cos xcex94xcex8 data ROM and the sin xcex94xcex8 data ROM, are required in view of its configuration.
The present invention is directed to solve the above problems, and it is an object of the present invention to provide a video signal processing apparatus which can reduce a circuit size in comparison with the conventional video signal processing apparatus as well as exhibit the performance which is equivalent to the conventional video signal processing apparatus.
To accomplish the above-described object, according to a first aspect of the present invention, a video signal processing apparatus which adjusts a hue of an image displayed on a display device when a video signal outputted from a video signal reception means is displayed on the display device comprises: address value output means which outputs an address value for adjusting the hue; addition means for generating a second address value corresponding to a phase value which has a predetermined phase difference from a phase value corresponding to a first address value by adding a predetermined value to the first address value outputted from the address value output means; selection means for selecting either the first address value which is outputted from the address value output means or the second address value which is outputted from the addition means; switching signal output means for outputting a switching signal for performing selection in the selection means to the selection means; storage means which previously stores data corresponding to the address value for adjusting the hue as well as decides the predetermined value, receives as an input the address value outputted from the selection means, and, when the inputted address value is the first address value, outputs the first data corresponding to the first address value, and when the inputted address value is the second address value, outputs the second data corresponding to the second address value; first latch means for preserving the first data, corresponding to the switching signal outputted by the switching signal output means; second latch means for preserving the second data, corresponding to the switching signal outputted by the switching signal output means; and hue adjustment means which adjusts the hue of the video signal received in the video signal reception means to output to the display device, by using the outputs of the first latch means and the second latch means.
Therefore, a single ROM can perform function of two ROMs. As a result, the video signal processing apparatus, which can reduce a circuit without losing performance in comparison with the conventional video signal processing apparatus, can be realized.
According to a second aspect of the present invention, in the video signal processing apparatus of the first aspect, data stored in the storage means in advance are in such a phase relation that a phase of first data corresponding to the first address value and a phase of second data corresponding to the second address value are of sinusoidal wave and cosine wave, respectively.
Therefore, the first and second data which are outputted from a ROM are loaded and held by a vertical synchronizing signal, whereby the sin xcex94xcex8 data and the cos xcex94xcex8 data are taken out from a single ROM. As a result, the video signal processing apparatus, which can reduce a circuit size without losing performance in comparison with the conventional video signal processing apparatus can be realized.
According to a third aspect of the present invention, the video signal processing apparatus of the first or second aspect, is provided with a load and hold circuit that comprises the first and second latch means, and is further provided with a flip-flop.
Therefore, the hue can be changed outside an effective screen area of the display device. Accordingly, an image, which has a uniform hue inside the effective screen area, can be always obtained.